A typical Electronic Article Surveillance (“EAS”) system in a retail setting may comprise a monitoring system and at least one security tag or marker attached to an article to be protected from unauthorized removal. The monitoring system establishes a surveillance zone in which the presence of security tags and/or markers can be detected. The surveillance zone is usually established at an access point for the controlled area (e.g., adjacent to a retail store entrance and/or exit). If an article enters the surveillance zone with an active security tag and/or marker, then an alarm may be triggered to indicate possible unauthorized removal thereof from the controlled area. In contrast, if an article is authorized for removal from the controlled area, then the security tag and/or marker thereof can be deactivated and/or detached therefrom. Consequently, the article can be carried through the surveillance zone without being detected by the monitoring system and/or without triggering the alarm.
The security tag or marker generally consists of a housing. The housing is made of a low cost plastic material, such as polystyrene. The housing is typically manufactured with a drawn cavity in the form of a rectangle. A bias magnet is disposed within the housing adjacent to one or more magnetoelastic resonator. The bias magnet is made of a semi-hard magnetic material. The resonator(s) is(are) made of a soft magnetic material in the form of an elongate thin ribbon produced by rapid quenching. During operation, the security tag or marker produces a resonant signal with a particular amplitude that is detectable by the monitoring system. Notably, markers with a single resonator have about 65% of the amplitude of markers with two resonators. As such, single resonator markers have reduced system performance as compared to dual resonator markers.
Common Acousto-Magnetic (“AM”) EAS markers are designed to provide maximum output signal in the smallest package possible in order to allow the markers to be placed on a wide range of products and hard goods. A key design element of these markers is the incorporation of a transverse curl to the resonator component(s) of the marker. This curl results in increased stiffness of the resonator which enhances the resonator's ability to overcome magnetic clamping and frictional damping due to the reduction in surface area contact between the resonator and the cavity surface.
However, certain product categories (including small, narrow items such as lipsticks and other cosmetics) are not easily tagged due to the narrow and/or curved nature of the packaging. Therefore, it is highly desirable to reduce the width of the AM EAS marker to something significantly smaller than the current, nominal width of 10.5 mm of most AM EAS marker (e.g., 5-7 mm) in order to expand the range of products capable of being tagged with the AM EA marker.
Attempts to create such a narrow label have been hindered by the difficulty in developing a resonator of the required dimensions with a transverse curl. Attempts to use a traditionally annealed, flat, resonator ribbon experience excessive clamping leading to reduced amplitude making the tag more difficult to detect, or requiring additional resonator components making the AM EAS markers more expensive.